code: def test_OLS():
      model = OLSModel(design=X)
      results = model.fit(Y)
      assert results.df_resid == 30
  
file_path: nipy/nipy/algorithms/statistics/models/tests/test_regression.py
imports: import numpy
  import scipy.linalg
  from numpy.testing import assert_array_almost_equal
  from ..regression import AREstimator, ARModel, OLSModel, ar_bias_correct, ar_bias_corrector, yule_walker
label_desc: Use image node_id 1 for calling a global function with example usage: test_OLS() without return types